Full Idea
Frankfurt says that basic issues concerning freedom of action presuppose and give weight to a concept of 'acting on a desire with which the agent identifies'.
Gist of Idea
Freedom of action needs the agent to identify with their reason for acting
Source
report of Harry G. Frankfurt (Freedom of the Will and concept of a person [1971]) by Wilson,G/Schpall,S - Action 1
Book Reference
'Stanford Online Encyclopaedia of Philosophy', ed/tr. Stanford University [plato.stanford.edu], p.2
A Reaction
[the cite Frankfurt 1988 and 1999] I'm not sure how that works when performing a grim duty, but it sounds quite plausible.